Increased capabilities of integrated-circuit chips (hereinafter referred to as IC chips) have led to increased input/output (I/O) densities and modified techniques for mounting IC chips to printed circuit (PC) boards involving IC chips. In view of the above, designs of IC test sockets for holding IC chips during their temporary connection to testing equipment are constantly being improved and modified. The existing lid-socket assemblies can roughly be divided into two main groups: (1) socket assemblies wherein the lid subassembly is separated from the socket sub-assembly and can be connected to the latter by clamps or locking mechanisms; and (2) socket assemblies wherein the lid sub-assembly is constantly pivotally connected to the socket.
For example, U.S. Pat. No. 5,865,639 issued in 1999 to M. Fuchigami, et al. describes a test socket that can be used for testing an electronic assembly. The test socket has a holder having a recess for receiving the electronic assembly. Heat sinks are pivotally secured to the holder and are biased from a loading position, wherein the electronic assembly can be located in the holder, to a testing position wherein the heat sinks contact the surface of an integrated circuit of the electronic assembly. Heat sinks have large mass and velocity, and therefore have kinetic energy when they strike an integrated circuit. Impact forces created by heat sinks on integrated circuits often result in damage to the integrated circuits.
The problem inherent in the test socket of the above patent is solved by U.S. Pat. No. 6,447,322 issued in 2002 to H. Yan. This patent describes a test socket for an electronic assembly that comprises a holder, a plurality of electric terminals, a heat sink, a compliant and thermally conductive thermal interface component, and a heat sink biasing device. The holder has a formation to receive the electronic assembly. The electric terminals are located on the holder, each for making contact with a respective electric contact and with the electronic assembly in order to test an integrated circuit of the electronic assembly. The heat sink is secured to the holder. The thermal interface component is attached to the surface of the heat sink. The heat sink biasing device has a first portion connected to the holder and a second portion connected to the heat sink, the second portion being biased relative to the first portion to move the heat sink from a loading position wherein the electronic assembly can be inserted into the holder, to a testing position wherein the heat sink is located next to the electronic assembly with the thermal interface component between the surface of the heat sink and the electronic assembly and contacting the electronic assembly.
In a majority of constructions, the lid assembly is pivotally connected to the socket, and the IC chip is held in the socket between the lid assembly and the socket by closing the lid and securing it in a closed position with the use of a clamping or locking mechanism. For example, U.S. Patent Application Publication No. 2006/0110953 published in 2006 (inventor T. Allsup) discloses an IC test socket where an IC chip is placed into the socket and is pressed to the socket seat by two pivotally connected lid members fixed in place by latching mechanisms.
U.S. Pat. No. 6,353,329 issued in 2002 to H. Kiffe discloses an integrated circuit test socket lid assembly that is intended for pivotal connection to the socket body by a hinge and is rotatable between a closed position and an open position. However, the lid assembly can be disconnected from the socket body without tools. The lid assembly includes a frame member secured to the hinge, and a pressure plate and actuation member contained within the frame member. The bottom surface of the pressure plate includes a plurality of channels extending from an open central portion to the circumference of the pressure plate for permitting thermal air flow over the integrated circuit. A preferred embodiment of the lid assembly provides a visual indication to the user when an integrated circuit is undergoing testing.
U.S. Pat. No. 5,808,474 issued in 1998 to J. Hively, et al. discloses a socket for testing an integrated circuit ball grid array package having external contacts formed by an array of solder balls. In this device, the lid that clamps the object to be tested in the socket is separated from the socket body and is fixed in place by flexible latching fingers that lock into recesses formed in the outer side walls of the socket body.
U.S. Pat. No. 6,710,612 issued in 2004 to W. Farnworth, et al. discloses a BGA test socket for use in standard testing and burn-in testing of BGA dice and method for testing such dice is disclosed wherein a die contact insert made of silicon or ceramic using standard IC fabrication technology is used. Through using such an insert, even small scale (pitch) BGA dice can be reliably tested including chip scale packaged (“CSP”) BGA dice. Furthermore, using such an insert allows a conventional socket to be adapted for use with a wide variety of both BGA dice and other varieties. A method for using the device is disclosed which overcomes current static electricity problems experienced in testing CSP BGA dice through closing the test socket before removing the die deposit probe.
An attempt to solve the problems of alignment and pressure application function is made in the device of U.S. Pat. No. 6,152,744 issued in 2000 to R. Maeda. This patent discloses a circuit socket having electrically conductive pads formed on a resilient circuitry component for contacting the terminals of an integrated circuit (IC) package which is positioned on the resilient circuitry. The electrically conductive pads are arranged around the center area of the resilient circuitry to be in one-to-one correspondence with the terminals of the IC package. The electrically conductive pads have individual circuit paths of substantially the same length and extend outwardly from the center area of the flexible circuitry. Additional electrically conductive pads are formed on the back side of the flexible circuitry in order to effect the required electrical connections to exterior circuits. These electrically conductive pads on the back side are connected to the conductor pattern on the front side by conductive through holes. With this arrangement all conductors have the same, reduced inductance. An insulative apertured film is preferably positioned intermediate to the IC package and to the flexible circuitry having the electrically conductive pads in order to perform certain alignment and pressure application functions.
Common drawbacks of known test sockets consist of insufficiently uniform pressure on the interface between the pusher and the IC chip in a clamped position of the chip, lack of self-alignment, insufficient removal of heat from the tested chips during the test, short service life of the lid-socket assembly in case of frequent use, and relatively long time required for setting an IC chip in the socket for testing.